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8 votes

Where does Planck's constant come from in non-renormalizability of quantum gravity?

One way to think about it is in terms of the path integral. For perturbative quantum gravity around flat space, we expand the metric as $$ g_{\mu\nu} = \eta_{\mu\nu} + h_{\mu\nu} $$ where $h_{\mu\nu}$ ...
Andrew's user avatar
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5 votes

What are natural units?

You already live in a world where natural units apply. The speed of light is exactly $1$ light-year/year, or equivalently $1$ light-second/second. Or approximately $1$ foot/nanosecond. This is useful ...
mmesser314's user avatar
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